1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and process for field testing automatic air valves in water and wastewater pipeline systems.
2. Description of the Related Art
The operation of water and wastewater pipeline systems may be severely impacted by the presence of air trapped in the pipeline. In fact, failure to properly de-aerate the line may lead to pump, valve, and pipe failures as well as faulty instrument readings.
Air in a pressurized, operating pipeline comes from three primary sources: air initially present in the line prior to startup, air or gas contained or generated within the water or wastewater itself, and air that enters the line through mechanical equipment.
Regardless of the source, the air present in the line tends to accumulate at high points in the line. This condition may lead to a host of problems in the pipeline, including line restriction, flow stoppage, or high pressure surge (water hammer).
In addition to the problem of trapped air in water and wastewater pipelines, vacuum or siphoning of the line may occur during a system shut down or failure. Such a condition may lead to line collapse or intensified surges in the pipeline.
To help alleviate the existence of trapped air or vacuum in water and wastewater pipeline systems, most municipalities employ automatic air valves at the high points in the line. Types of automatic air valves include air/vacuum valves, air release valves and combination air valves.
An air/vacuum valve exhausts large quantities of air upon system start-up, as well as allowing air to re-enter the line upon system shut down or system failure. As water enters an air/vacuum valve, a float rises, closing a discharge port. The port, and hence the valve, will remain closed until the air pressure in the valve drops to atmospheric pressure. Furthermore, if a negative pressure develops in the line, the valve opens, admitting air into the line and preventing the deleterious effect of vacuum or siphoning in the system.
An air release valve continuously releases accumulated air during system operation. Similar to the air/vacuum valve, a float closes a discharge port as the water rises in the valve. During operation, as air from the line enters the valve, it displaces the water. As a result, a float drops from its sealed position against the discharge port, allowing the air to release to the atmosphere. As the air is vented, it is replaced by water, raising the float and closing the valve. As air accumulates, the valve continues to cycle in this manner to remove the collected air.
A combination air valve performs the functions of both an air/vacuum valve and an air release valve. Therefore, the combination air valve exhausts large quantities of air on start-up, admits air on shutdown or failure, and releases air continuously during operation.
However, as important as these valves are to the proper functioning and life of water and wastewater pipeline systems, a shortage of apparatus and procedures exist for ensuring proper functioning of these valves in the field. Accordingly, a need exists for improved apparatus and processes for testing automatic air valves in water and wastewater pipeline systems.